Diaphragm-type fluid flow regulators comprise a housing with a chamber therein and an inlet and an outlet. A valve regulates flow between the inlet and the outlet. A diaphragm in the chamber is connected to the valve so that movement of the diaphragm operates the valve. The chamber is vented to allow air to flow into and out of the chamber to accommodate movement of the diaphragm.
In some instances the air flow through the vent is restricted in order to slow the movement of the diaphragm. One method of restricting vent flow is to provide a small aperture. However, it is expensive to accurately form small apertures. Moreover, these apertures can become blocked by dirt or debris, and the flow rate (and thus the diaphragm speed) cannot be adjusted. Another method of restricting vent flow is with a needle valve. While needle valves do provide adjustability, they are expensive and are also subject to being blocked by dirt and debris.